If you have cancer, HIV, diabetes, lupus, depression, heart disease—or you simply look up health-related information online—advertisers are watching you. A new paper on what happens when users search for health information online shows that some of our most sensitive internet searches aren’t as anonymous as we might think.

Marketers care very much about what diseases and conditions people are searching for online. Tim Libert, a doctoral student at the Annenberg School For Communication at the University of Pennsylvania and the author of the paper says that over 90% of the 80,000 health-related pages he looked at on the Internet exposed user information to third parties.